How can I select a bone by name using python in blender 2.8
Find the object first (by name if you wish), then access the armature. The armature is the data of the object. It has an edit_bones property, but this property is only available in edit mode. This means we have to switch to edit mode first.

import bpy

ob = bpy.data.objects['Armature']
armature = ob.data

bpy.ops.object.mode_set(mode='EDIT')

# get specific bone name 'Bone'
myBone = armature.edit_bones['Bone']
#print the position of its head
print(myBone.head)

# loop through all bones
for bone in armature.edit_bones:
    # move its head and tail
    bone.head.x += 1.5
    bone.tail.x += 1.5


bpy.ops.object.mode_set(mode='OBJECT')